Possible cyst on my easter egger

I have an Easter Egger that has developed a large and what seems to be a liquid filled cyst just above her breast at the base of her neck. I'm sure what it is? My first insincere is to drain it, but I definitely don't want to make it worse. It's been there about a week and a half. It doesn't seem to be affecting her at all. She's still active, eating and drinking, foraging etc. Any ideas on what it could be and what I should do?

That looks like an overfull crop. I'd isolate her and withhold food for at least 12 hours for observation. If the crop reduces in size, she's probably just a piggy eater. If there is no change, I would suspect either sour crop or impacted crop.